Preventative Medicine

Veterinary preventative medicine

• focuses on improving the health of animal populations and individuals

• detection, prevention, and control of diseases impacting animals, food, and humans

• collaboration between animal + human heath professionals, private NGOs, & government agencies

Levels of prevention

1. primary: interventions targeting healthy individuals/populations in an attempt to prevent exposure to disease (ex: vaccines)

2. secondary: early detection & rapid treatment of disease to minimize impact (ex: annual exams/tests)

3. tertiary: managing & stopping/slowing disease progression to improve quality of life (ex: rehab)

Population medicine

• surveillance (monitor trends to detect risk) → intervention → evaluation (measure impact of intervention)

• ex: herd vaccination, biosecurity, reproductive management, nutritional management, culling

• protects pets, livestock, ecosystems, & humans

• influences health at the individual level

Individual medicine

• diagnose/identify → treatment → monitor/follow-up

• patient-focused

• ex: regular vet visits, vaccines/parasite prevention, spay/neuter

Epidemiology

• study of disease patterns

• ex: mapping virus outbreaks

Biostatistics

• data analysis for decision-making

• ex: calculating vaccine efficacy/making autogenous vaccines

Infectious/parasitic disease

• study of natural history of disease

• ex: avian influenza surveillance

Food protection

• ensuring safe animal products

• ex: meat processing

Environmental health

• managing ecological risks

• ex: wildlife-livestock interface management

Public health administration

• protecting human health via animals

• ex: rabies control

Client education

• clear/effective communication about recommendations

• addressing owner questions/misconceptions

• providing resources (handouts, websites)

• challenges: owner compliance, cost concerns/access to care

Causes of veterinary injuries

• animal bites/scratches

• exposure to toxic substances

• sprains/strains/repetitive motion injuries

• hearing loss

• allergy development

World Organization for Animal Health (WOAH)

• UN agency for animal health organized by regional offices

• Terrestrial and Aquatic Animal Health Codes/Manuals - safe international trade + diagnosis of diseases

• unlikely for vets to interact directly

World Health Organization (WHO)

• UN agency for human health organized by regional offices

• works with infectious/chronic disease, food safety, & antibiotic resistance

• sets International Health Regulations for response to international spread of disease

USDA APHIS

• federal animal health agency

• programs include:

  • animal care - animal welfare & horse protection acts

  • veterinary services - animal health protection & virus serum toxin acts

  • wildlife services - manage wildlife related problems

• vets interact with programs daily - reporting animal disease, using regulated biologics

• state equivalent = ODA

USDA FSIS

• federal animal & human health agency

• prevents illness from meat & egg products (inspection)

HHS CDC

• federal human health agency

• protects from foreign and domestic health & safety threats

• provides information about zoonotic diseases (National Center for Emerging & Zoonotic Infectious Diseases)

• vets unlikely to interact directly

• state equivalent = ODH

HHS FDA

• federal human health agency

• food, drug, and cosmetics & food safety modernization acts

• ensures safety & efficacy of human + vet medicines, biologics, & devices/radiation-emitting products

• vets likely to interact with regulated products daily

EPA

• regulates insecticides, rodenticides, flea/tick products, & disinfectants

• likely to interact with regulated products daily

• state equivalent = same name

DOJ DEA

• regulates manufacture & distribution of controlled pharmaceuticals + listed chemicals

• vets likely to be regulated by agency to prescribe/dispense controlled substances

• state level equivalent = board of pharmacy

OSHA

• regulatory agency within US Department of Labor that sets/enforces labor standards

• visits practices when invited (no fine) or when complaint is filed (fine)

NIOSH

• part of CDC within the US Department of Health and Human Services responsible for conducting research & making recommendations for prevention of work-related injury/illness

• visits practices when invited by employer/employee/union

Employer responsibilities

• ID and assess hazards

• make employees aware of risks

• eliminate/mitigate risks

• maintain records of workplace injuries/illnesses/deaths (does not apply to small businesses)

PPE

• for hazards that cannot be fully mitigated

• needs to be provided at no charge to employees & must fit

• employees trained in proper use

Respirators

• type of protection must align with hazard

• sealed fit required (not surgery masks!)

Ionizing radiation standards

• ensure occupational doses not exceeded

• supply appropriate monitoring tools (dosimeters)

• survey hazards & post warning signs

Hazard communication standard

• all chemicals (and secondary containers) must have labels & safety sheets

• SDS must be accessible to all employees

• employees trained to handle appropriately

General duty clause

• provide a work environment free from recognized hazards that are causing or likely to cause death/physical harm

• hazard is foreseeable and recognized by employer/injury/common sense

Hazard

• something with the potential to hurt a person

Risk

• the likelihood of a hazard actually causing harm

Population

• a group of animals inhabiting the same general area

• usually the same species

Health

• a state of complete physical, mental, & social wellbeing

Disease

• any harmful deviation from normal structure or function

Infection

• invasion & multiplication of microorganisms in bodily tissues

Infectious disease

• consequences of infection

• impairs the normal state of the organism, interrupts/modifies normal function

Communicable Disease

• illness due to specific infectious agent (or toxic products) arising through transmission from an infected organism or inanimate reservoir to a susceptible host

• can be direct or indirect via intermediate host, vector, or object

Animal Disease Traceability

• established by USDA

• must have official ID & certificate of veterinary inspection to move livestock interstate

• must record ID on movement documentation

Health certificate

• USDA accredited vet certifies animal has been inspected & is healthy/free of contagious disease

• federal level International Health Certificate, state level Certificate of Veterinary Inspection

Official ID

• visual ear tag w/Animal Identification Number, ear tag shield, manufacturer’s logo, & “unlawful to remove”

• may or may not have RFID tech

Permanent IDs

• radio frequency ID/microchip

• tattoos/brands

• ear notches (swine)

• can be considered official IDs on species-specific basis

Temporary IDs

• hide marks (chalk, wax pen, paint)

• stall cards (equine)

• USDA backtags

• collars

Trace-back

• identify origin of agent/hazard

• tracks any animal, product, or vector that has been moved onto an infected premises

Trace-forward

• identify potential downstream premises

• tracks any animal, product, or vector that has been moved from an infected premises

Tracing

• data tracking of livestock contagious diseases to inform management protocols (welfare, nutrition, repro, etc.)

• early detection/warning allows prompt implementation of disease controls to restore/protect herd health

Population health assessment

• systematic assessment of health, welfare, & current practices within a group of animals

• findings inform management + preventative medicine recommendations

• can lead to risk/problem investigation if issues found

• GP equivalent - wellness exam

PHA benefits

• reduce incidence of disease in population

• decrease treatment costs & mortality rates

• improve animal welfare/QOL

• increase productivity & profit

Site visit protocol

1. evaluate outside of animal area (maintenance, biosecurity risks, public access/traffic patterns)

2. evaluate inside animal area (ventilation, stocking density, general health/magnitude of issues)

3. evaluate individual pens (overall behavior, sizes, mobility issues, food/water)

4. evaluate individual animals (physical exam, BCS, ID individuals that need treatment/diagnostic testing)

5. view records/ask questions

SOAP

• subjective: population description, history, preventative medicine in use, reason for visit

• objective: calculated/estimated morbidity/mortality rates, results from recent disease surveillance records, diagnostic test results

• assessment: problems IDed, diagnoses

• plan: recommendations, further investigation, follow-up action/education

Epidemiology

• human & animal ecology as relating to states of health

• assumes that disease does not occur at random, has observable causal & preventive factors, & has occurrence related to environment of species

• host-agent-environment triad

Infectivity

• ability of etiologic agent to penetrate & reproduce in a host

• proportion of exposed that become infected

• DOES NOT IMPLY DISEASE

Pathogenicity

• ability of etiologic agent to cause disease

• proportion of infected that develop clinical disease

Virulence

• ability of etiologic agent to cause severe disease/death

• proportion of infected that develop severe disease/death

Host

• organism capable of becoming infected with & diseased by agent under natural conditions

• survival ± development/replication of agent can occur

Natural host

• maintains infection in endemic state

Dead-end host

• does not normally transmit agent

Amplifier host

• supports rapid multiplication of agent

Reservoir

• where agent normally lives/grows/multiplies - agent depends on for survival

• typically do not show signs of illness

• serves as common source of infection in susceptible hosts

Chain of infection

• portal of exit from infected reservoir into portal of entry into susceptible host

• portals of exit: aerosols, feces, urine, blood

• portals of entry: respiratory system, GI tract, broken skin

Horizontal transmission

• touch/bite/scratch

• contaminated droplets/bodily fluids

Vertical transmission

• mother-to-offspring via placenta/mammary

Direct transmission

• spread through contact of infected animal (or its bodily fluids) with open wounds/mucous membranes

• ex: droplet/aerosol projection (short-range),

Indirect transmission

• spread through intermediary vehicle/vector

• vehicles: fomites, ingestion of contaminated food/water, biological products

• vectors: arthropods, may support multiplication/development of agent (biological) or not (mechanical)

• ex: airborne (long-range)

Host factors

• level of contact/exposure

• young, old, pregnant, immunocompromised

Endemic

• disease occurs at an expected frequency

Epidemic

• disease occurs at greater than expected frequency

Sporadic

• disease occurs occasionally in single cases or small clusters

Problem investigation

• targeted assessment of group health/welfare to investigate & address a specific problem

• done to address perceived/real increase in disease frequency, production issues, or husbandry/management issues

• GP equivalent = sick exam

Outbreak investigation steps

1. gather info

   1. who, what, where, when (age + time of year), how many (morbidity/mortality, prevalence/incidence)

2. verify problem exists

3. establish case definition (animals representative of problem)

4. plan investigation

5. form hypothesis

6. test hypothesis (based on plausibility, deficiency relative to a standard, & evidence)

7. design intervention (practical, feasible, considering labor inputs + opportunity cost)

Surveillance

• systematic collection, analysis, & interpretation of data measuring magnitude, changes, & trends + dissemination of information = take action/intervene

• targets agents/diseases for which rapid, direct, predetermined action is warranted to control/prevent

Monitoring

• surveillance without intervention threshold

Screening

• testing apparently healthy animals to confirm negative status & ID previously unknown infected individuals

Early detection

• ID disease rapidly before significant spread to facilitate disease control

• surveillance should be continuous, representative of population, & sensitive to rare cases

Demonstrate freedom

• prove that disease is not present in population (trade/ending control measures)

• surveillance can be ad hoc/intermittent, risk-based, & designed to detect higher prevalence

Case finding

• ID infected animals/herds during control program

• surveillance should be comprehensive, ongoing, & sensitive

Measuring disease

• detect changes in level of disease in population

• surveillance can be ad hoc/periodic & based on a large + representative sample

Surveillance agencies

• human: state dept. of health, CDC, FDA

• animal: state dept. of ag, USDA APHIS, NAHLN

Passive surveillance

• uses samples/observations primarily collected for another purpose

• more efficient but possibility of incomplete data

Active surveillance

• uses samples/observations collected specifically for program use

• higher levels of completeness but more expensive to maintain

• needed for rare/hard to detect diseases

Antibiogram

• periodic summary of antimicrobial susceptibility results for selected pathogens recovered from a defined population

• can provide info about local antimicrobial resistance & inform treatment choice

• an example of passive surveillance

Prevention

• steps taken to lower risk of infection before agent is present (not letting infectious agent in)

• ex: foot & mouth, African swine fever

Control

• measures taken to lower risk of exposure/frequency of infections & decrease severity of disease (occurs when infectious agent is in the population)

• aim is to reduce impact of disease to tolerable level

Elimination

• reduction to zero of incidence of infection caused by a specific agent in a defined area as a result of deliberate efforts

• continued measures required to prevent re-establishment of transmission

• necessary conditions: effective diagnostic test, destruction of agent in reservoirs (or of reservoirs), small host range, limited spectrum of disseminating mechanisms, acceptability to industry

Eradication

• permanent world-wide reduction to zero of incidence of infection caused by a specific agent as a result of deliberate efforts

• intervention no longer required

Extinction

• specific infectious agent no longer exists (in nature or lab)

Diagnostics

• direct: detects pathogen itself

  • antigen detection (ELISA)

  • nucleic acid detection (PCR)

  • visualization (parasites)

  • culture/isolation (bacteria)

• indirect: detects response to a pathogen, not conclusive

  • antibody detection (increase over time)

Biosecurity

• preventative measures designed to reduce risk of transmission of infectious diseases (herds/facilities)

• bioexclusion (keeping out) vs biocontainment (keeping in)

Biosafety

• practices designed to protect ourselves from harm

Infectious dose

• amount of pathogen required to cause infection in host

• low ID50 = high virulence

• ID50 = amount of organism required to infect 50% of population

Test & remove

• test all animals & remove positives

• limits: percentage of animals involved, amount of disruption to economy, availability of replacement animals, sensitivity/specificity of diagnostic test

• should use a highly sensitive test

Sensitivity

• catches all positives but creates many false positives

• rule out

Specificity

• does not catch all positives but has very few false positives

• rule in

Depopulate

• elimination of diseased animals & all animals in contact during the incubation period

• indicated with fast-moving disease

• should use a highly specific test

Treatment

• must be very effective in killing agent

Vaccination

• vaccinate all animals/susceptibles in population

• aims to reduce clinical signs, carriage, disease transmission, & antibiotic usage

• used when prevalence is high, aims to drive down over time

• need to be able to differentiate disease status from vaccinated status (direct diagnostics)

Strategies for vector-borne diseases

• create barriers

Conceptual biosecurity

• primary level - set-up of animal facilities (location)

• most effective way to limit risk: physical isolation, distance from other animals/roads, limited use of vehicles/facilities & access of personnel

• control spread by vermin, wild animals, & wind

Structural biosecurity

• secondary level

• physical factors - layout, perimeter fencing, drainage, changing rooms/showers, air filtration

• long-range planning should consider on-site movement

Procedural biosecurity

• tertiary level

• prevent introduction & spread of infection in a facility

• processes & activities should be reviewed constantly

Perimeter buffer area

• controlled area around animal areas/buildings to reduce contamination & protect animals

• control entry of vehicles, equipment, & people

Line of separation

• internal control boundaries (barriers, signage)

• some biosecurity action must be taken before crossing the line